JP6589593B2 - METHOD, EVALUATION PROGRAM, AND IMAGE FORMING APPARATUS FOR EVALUATING STATUS OF COMPONENTS RELATED TO A PROCESS CONTAINING AT LEAST CHARGING AND FORMING OF ELECTROSTATIC LATERIAL - Google Patents

Description

  This disclosure relates to an image forming apparatus, and more particularly, to state evaluation of elements constituting the image forming apparatus.

  An image forming apparatus according to an electrophotographic system forms an electrostatic latent image on a photoconductor as an image carrier, and forms a toner image by adhering toner to the formed electrostatic latent image. This photoreceptor is a consumable that gradually deteriorates under the influence of light fatigue and surface wear due to a cleaning blade.

  With regard to the technology for determining the lifetime of the photoreceptor, Japanese Patent Laid-Open No. 10-39691 (Patent Document 1) has a plurality of bias application conditions applied to charging means for charging the photoreceptor, and a bias corresponding to the application condition. A configuration is disclosed in which an integrated value of the application time is calculated, a coefficient that differs for each bias application condition is multiplied by the integrated value, and the sum of these values is taken as the damage index of the electrophotographic photosensitive member. When the damage index exceeds a predetermined value, it is determined that the life of the photosensitive member has come.

  Japanese Patent Laid-Open No. 2011-28102 (Patent Document 2) discloses that each AC current value that flows through a charging roller is applied a plurality of times by applying a plurality of charging voltages in which a predetermined AC voltage is superimposed on each DC voltage having a different voltage value. In which the state of the photoconductor is determined based on the difference between the AC current values.

JP 10-39691 A JP 2011-28102 A

  However, the technique disclosed in Patent Document 1 does not take into account the effects of external environmental conditions such as temperature and humidity during printing, the printing rate, and the number of continuous prints, and is substantially equivalent to the life based on the damage index. There is a possibility that the service life will deviate.

  In addition, since the technique disclosed in Patent Document 2 determines the lifetime based on the film thickness of the photoconductor, these abnormalities are detected when local contamination or abrasion occurs on the photoconductor. It may not be possible.

  In addition, the techniques disclosed in Patent Documents 1 and 2 cannot determine the lifetime (abnormality) of components other than the photoreceptor.

  The present disclosure has been made in order to solve the above-described problems, and an object in one aspect is to make the state of components related to a process including at least charging and formation of an electrostatic latent image more than conventional. It is to provide a method for highly accurate evaluation. Another object of the present invention is to provide a program for evaluating a state of a component related to a process including at least charging and formation of an electrostatic latent image with higher accuracy than before. Another object of the present invention is to provide an image forming apparatus that evaluates the state of components related to a process including at least charging and formation of an electrostatic latent image with higher accuracy than before.

A method for evaluating a state of a component related to a process including at least charging and formation of an electrostatic latent image, which is used for image formation in accordance with an electrophotographic method, and charging the image carrier by applying a first DC voltage A step of exposing the image carrier charged by the application of the first DC voltage in a uniform pattern; and a step corresponding to the uniform pattern by adhering toner to the exposed image carrier. Detecting a density in the sub-scanning direction at a predetermined position in the main scanning direction of the first toner image, and calculating a displacement width of the density from the detected maximum value and minimum value; A step of applying an alternating voltage including a second DC voltage and an AC voltage to charge the image carrier, and a step of exposing the image carrier charged by the application of the alternating voltage in a uniform pattern. Forming a second toner image corresponding to the uniform pattern by adhering the toner to the image carrier charged with the alternating voltage and exposed in the uniform pattern; and the second toner Detecting a density in the sub-scanning direction at a predetermined position in the main scanning direction of the image, calculating a density displacement width from the detected maximum value and minimum value, and a density calculated for the first toner image; And displaying a warning screen indicating that an abnormality has occurred in the component when the displacement width is equal to or greater than the displacement width of the density calculated for the second toner image .

Preferably, the method further includes the step of setting a predetermined density range in association with the uniform pattern. In the step of displaying the warning screen, the density displacement width calculated for the first toner image is equal to or larger than the density displacement width calculated for the second toner image, and the first toner image is displayed. When the density change in the sub-scanning direction at a predetermined position in the main scanning direction is not within the predetermined density range , a warning screen is displayed .

More preferably, setting to step includes based on the displacement amount of concentration change in the second toner image, to determine a predetermined concentration range.

  More preferably, the absolute value of the first DC voltage is greater than the absolute value of the second DC voltage.

More preferably, the value of the first DC voltage is set based on the value of the second DC voltage and the amplitude of the AC voltage.

Preferably , based on the difference between the maximum value in the density of the first toner image and the upper limit value of the predetermined density range, or the difference between the minimum value in the density of the first toner image and the lower limit value of the predetermined density range. The method further includes the step of determining the degree of deterioration of the component.

Preferably , if it is determined that the density of the first toner image in the sub-scanning direction is not within the predetermined density range, whether or not a position outside the predetermined density range corresponds to a predetermined period is further determined. The step of determining is further provided . The predetermined cycle includes a cycle corresponding to at least one of the rotation cycle of the component rotating in contact with the image carrier and the rotation cycle of the image carrier.

More preferably, further comprising a Jo Tokoro concentration range position when a decision is made to correspond to a predetermined period, to identify the components that are degraded from the corresponding predetermined period.

Preferably, further comprising the steps of printing a first toner image on the first recording medium, and printing the second toner image on the second recording medium.
Preferably, the component includes an image carrier and a charging device for charging the image carrier.

  More preferably, the component further includes a developing device for attaching the toner image to the image carrier.

Preferably, the density of the first toner image and the density of the second toner image are the density of the toner image formed on the image carrier.
Preferably, the image forming apparatus includes an intermediate transfer member that receives and conveys the toner image formed on the image carrier and transfers the toner image to a recording medium. The density of the first toner image and the density of the second toner image are the density of the toner image transferred to the intermediate transfer member.

Preferably, the uniform pattern is a pattern composed of halftones.
According to another aspect, the program causes the computer of the apparatus that performs image formation to execute the above method .

According to another aspect, an electrophotographic image forming apparatus includes a control unit, a display unit, an image carrier that carries a toner image, a charging device that charges the image carrier, and a first charging device . A power supply device for applying a direct current voltage, an exposure device for exposing the image carrier charged by the application of the first direct current voltage in a uniform pattern, and attaching toner to the exposed image carrier. And a developing device for forming a first toner image corresponding to such a pattern. The power supply device applies an alternating voltage including the second DC voltage and the AC voltage to the charging device. The exposure apparatus exposes the image carrier charged by application of alternating voltage in a uniform pattern. The developing device forms a second toner image corresponding to the uniform pattern by adhering the toner to the image carrier charged with the alternating voltage and exposed in the uniform pattern. The control unit detects the density in the sub-scanning direction at a predetermined position in the main scanning direction of the first toner image, thereby calculating a density displacement width from the detected maximum value and minimum value. The control unit detects the density in the sub-scanning direction at a predetermined position in the main scanning direction of the second toner image, thereby calculating a density displacement width from the maximum value and the minimum value of the detected density. When the displacement width of the density calculated for the first toner image is equal to or larger than the displacement width of the density calculated for the second toner image, the control unit relates to a process including at least charging and formation of an electrostatic latent image. A warning screen indicating that an abnormality has occurred in the component to be displayed is displayed on the display unit .

  A method for assessing the state of a component associated with a process that includes at least charging and forming an electrostatic latent image, according to one embodiment, can assess the state of the component with greater accuracy than previously.

FIG. 6 is a diagram for explaining a surface potential and a toner density of a photosensitive member depending on a charging method. It is a figure explaining the image pattern by the difference in a charging system. It is a figure explaining the structural example of the image forming apparatus according to an embodiment. It is a figure explaining the charging roller according to an embodiment. It is a figure explaining the power supply device according to an embodiment. It is a figure explaining the structure of the control part according to embodiment. It is a flowchart explaining the evaluation method according to an embodiment. It is a figure explaining the test | inspection image according to embodiment. It is a figure explaining the change of the toner density according to the embodiment. It is a figure explaining the change of the toner density according to another embodiment. It is a flowchart explaining the evaluation method according to other embodiment. It is a flowchart explaining the evaluation method according to other embodiment. It is a block diagram explaining the functional structure of CPU. FIG. 6 is a diagram for explaining a change in toner density. It is a flowchart explaining the evaluation method according to other embodiment. It is a flowchart explaining the evaluation method according to other embodiment. It is a figure explaining the test | inspection image according to a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<A. Introduction>
FIG. 1 is a diagram for explaining the surface potential and toner density of a photoreceptor depending on the charging method. In FIG. 1A-1, a voltage including a DC voltage and an AC voltage (hereinafter also referred to as “alternating voltage”) is applied to the charging roller to charge the photosensitive member. FIG. 1A-2 is a diagram in which the surface potential of the photosensitive member charged by the charging roller with respect to the point A is plotted clockwise.

  In the charging method for applying an alternating voltage, a positive discharge and a negative discharge are alternately generated between the charging roller and the photosensitive member, so that the surface of the photosensitive member can be uniformly charged at a desired potential. . Therefore, as shown in FIG. 1A-2, the surface potential of the photoconductor can be uniformly charged even if a certain amount of dirt or scraping exists on the photoconductor. As a result, the density of the toner image developed on the photoconductor becomes uniform even if the photoconductor has a certain amount of dirt and scrapes.

  On the other hand, in FIG. 1B-1, only the DC voltage is applied to the charging roller to charge the photosensitive member. The charging method in which only a DC voltage is applied generates only a positive / negative discharge. Therefore, as shown in FIG. 1 (b-2), when dirt or scraping exists on the photosensitive member, the electric field strength formed between this portion and the charging roller varies, and the surface potential is changed. Becomes non-uniform. As a result, the density of the toner image formed on the photoconductor becomes non-uniform according to dirt or scraping.

  The cause of the non-uniform surface potential of the photoconductor is due to the charging roller and the cleaning blade (not shown) in contact with the photoconductor, in addition to the photoconductor surface depletion, scratches, dirt, etc. There is. For example, the cause of the charging roller may be an increase in the resistance of the charging roller, a mirror surface due to a decrease in the friction coefficient, scratches, dirt, and the like. For example, the cause of the blade is blade wear.

  According to the above, when some state abnormality has occurred in the photoconductor, the charging roller, etc., the density variation of the toner image formed on the photoconductor is greater in the charging method using the DC voltage than in the charging method using the alternating voltage. Is noticeable.

  Using this property, the state (degradation level) of the photoconductor, charging roller and blade can be detected with high sensitivity by measuring the toner density formed on the photoconductor using a DC voltage charging method. it can.

  FIG. 2 shows an example of an image pattern when a charging method using an alternating voltage and a DC voltage is used. 2A to 2F are image patterns obtained by developing a common uniform electrostatic latent image.

  FIG. 2A shows an image pattern when the photosensitive member is charged by applying an alternating voltage to the charging roller. As described above, even if there is some abnormality in the state of the photoconductor, the charging roller, etc., the surface potential of the photoconductor is formed uniformly, so that the image density (toner density) becomes uniform.

  FIGS. 2B to 2F show image patterns when only the DC voltage is applied to the charging roller to charge the photosensitive member. If there is an abnormality in the state of the photoconductor or charging roller, the surface potential of the photoconductor becomes non-uniform. Since a toner image is formed on the photoconductor according to the unevenness of the surface potential, the image density becomes nonuniform as shown in FIGS.

  For example, if the photoconductor is scraped in the axial direction, or if dirt is attached in the axial direction of the charging roller, a horizontal stripe (main scanning) having periodicity as shown in FIG. Direction streaks).

  In this way, by using a charging system using a DC voltage, abnormalities in the state of the photoconductor, the charging roller, etc. can be made obvious and detected with high sensitivity. Hereinafter, a method for evaluating the state of the photoconductor and the charging roller using this property will be described.

<B. Embodiment 1-Determination Based on Variation of Concentration Range>
(B1. Image forming apparatus 100)
FIG. 3 is a diagram illustrating a configuration example of the image forming apparatus 100 according to the embodiment. The image forming apparatus 100 is an electrophotographic image forming apparatus such as a laser printer or an LED printer. As shown in FIG. 3, the image forming apparatus 100 includes an intermediate transfer belt 1 as a belt member at a substantially central portion inside. Below the lower horizontal portion of the intermediate transfer belt 1, four image forming units 2Y, 2M, 2C, and 2K corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors, respectively. Are arranged side by side along the intermediate transfer belt 1, and have drum-type photoreceptors 3Y, 3M, 3C, and 3K as image carriers.

  Around each of the photoreceptors 3Y, 3M, 3C, and 3K, blades 11Y, 11M, 11C, and 11K, contact charging type charging rollers 4Y, 4M, 4C, and 4K, and an exposure apparatus are sequentially arranged along the rotation direction. Print head portions 5Y, 5M, 5C, 5K, developing devices 6Y, 6M, 6C, 6K corresponding to the developing rollers 6YR, 6MR, 6CR, 6KR, density sensors 7Y, 7M, 7C, 7K, and intermediate Primary transfer rollers 8Y, 8M, 8C, and 8K that face the photoreceptors 3Y, 3M, 3C, and 3K across the transfer belt 1 are disposed.

  Each of the charging rollers 4Y, 4M, 4C, and 4K is provided with cleaning rollers 9Y, 9M, 9C, and 9K for cleaning the surface of the roller, and further, power supply devices 10Y, 10M, and 10C that supply power to the charging rollers. It is electrically connected to 10K.

  In each of the image forming units 2Y, 2M, 2C, and 2K, the respective photoreceptors 3Y, 3M, 3C, and 3K, charging rollers 4Y, 4M, 4C, and 4K, cleaning rollers 9Y, 9M, 9C, and 9K, and blades The photoconductor units 12Y, 12M, 12C, and 12K including the units 11Y, 11M, 11C, and 11K are configured to be detachable from the image forming apparatus 100.

  A portion of the intermediate transfer belt 1 supported by the intermediate transfer belt driving roller 14 is in pressure contact with the secondary transfer roller 15, and secondary transfer is performed in this region. A fixing heating unit 18 having a fixing roller 16 and a pressure roller 17 is disposed at a downstream position of the conveyance path R1 behind the secondary transfer region. Fixing and heating are performed by a pressure contact portion between the fixing roller 16 and the pressure roller 17.

  A paper feed cassette 30 is detachably disposed below the image forming apparatus 100. The sheets P stacked and accommodated in the sheet feeding cassette 30 are sent out one by one from the uppermost one to the transport path R1 by the rotation of the sheet feeding roller 31.

  In this embodiment, the image forming apparatus 100 employs an intermediate transfer method having a plurality of image forming units (2Y, 2M, 2C, 2K) as an example. However, the present invention is not limited to this. The image forming apparatus may be an electrophotographic system. Specifically, the image forming apparatus may include a single image forming unit or a rotary system.

  Further, although charging rollers (4Y, 4M, 4C, 4K) are used as charging means for the photosensitive member, the invention is not limited thereto, and for example, a contact charging type charging brush, a non-contact charging type corona discharge device, or the like is used. May be.

  In addition, although the photosensitive member unit includes a photosensitive member, a charging roller, a cleaning roller, and a blade, the present invention is not limited to this. For example, the arbitrary components of the photosensitive member, the charging roller, and the image forming unit are included. The photoreceptor unit may be configured to be detachable.

  Further, the blades 11Y, 11M, 11C, and 11K are not necessarily mounted on the image forming apparatus 100, and may not be mounted.

(B2. Schematic operation of image forming apparatus 100)
Next, a schematic operation of the image forming apparatus 100 having the above configuration will be described. When an image signal is input from an external device (for example, a personal computer) to the control unit 70 of the image forming apparatus 100, the control unit 70 creates a digital image signal obtained by color-converting the image signal into yellow, cyan, magenta, and black. Then, based on the input digital signal, the print head units 5Y, 5M, 5C, and 5K of the image forming units 2Y, 2M, 2C, and 2K are caused to emit light to perform exposure.

  As a result, the electrostatic latent images formed on the photoreceptors 3Y, 3M, 3C, and 3K are developed by the developing units 6Y, 6M, 6C, and 6K, respectively, and become toner images of the respective colors. The density sensors 7Y, 7M, 7C, and 7K are respectively arranged at the centers of the photoconductors 3Y, 3M, 3C, and 3K in the axial direction. Detect. In this example, as an example, the density sensor includes a light-emitting element (not shown) that emits light and a light-receiving element (not shown) that receives reflected light emitted and reflected from the light-emitting element. Let it be an optical sensor. When light is emitted from the light emitting element of each density sensor to the surface of the photoreceptor, the light receiving element detects reflected light reflected by the toner image on the photoreceptor. Based on the photocurrent (detection voltage) generated in the light receiving element, the density of the toner adhering to the photoconductor is detected.

  In this example, only one density sensor is arranged, but a plurality of density sensors may be arranged. For example, one (a total of two) may be arranged near both ends in the axial direction of the photosensitive member. Further, the density sensor is a line sensor, and may monitor the entire width of the photosensitive member in the axial direction.

  The toner images of the respective colors are primarily transferred in a superimposed manner on the intermediate transfer belt 1 that moves in the direction of arrow A in FIG. 1 by the action of the primary transfer rollers 8Y, 8M, 8C, and 8K.

  After the primary transfer, the photoreceptors 3Y, 3M, 3C, and 3K are cleaned by slightly removing the toner remaining on the surface with the blades 11Y, 11M, 11C, and 11K.

  The toner image formed on the intermediate transfer belt 1 in this way is secondarily transferred collectively onto the paper P by the action of the secondary transfer roller 16.

  The toner image secondarily transferred to the paper P reaches the fixing heating unit 18. The toner image is fixed on the paper P by the action of the fixing roller 16 and the pressure roller 17. The paper P on which the toner image is fixed is discharged to the paper discharge tray 60 via the paper discharge roller 50.

(B3. Charging roller)
Next, the structure of the charging roller will be described with reference to FIG. Each of the charging rollers 4Y, 4M, 4C, and 4K includes a core metal 21Y, 21M, 21C, and 21K at the center of the inside, and conductive elastic layers 22Y, 22M, 22C, and 22K are disposed around the cores. Surface layers 23Y, 23M, 23C, and 23K including roughness particles are disposed on the outer periphery of each conductive elastic layer.

  The conductive elastic layers 22Y, 22M, 22C, and 22K are, for example, epichlorohydrin rubber (ECO, CO, etc.), nitrile rubber (NBR), ethylene propylene diene rubber (EPDM), silicone rubber, urethane rubber, styrene-butadiene rubber (SBR). ), Isoprene rubber (IR), chloroprene rubber (CR), natural rubber (NR), and the like. These materials may be used alone or in combination of two or more. Of the above materials, ethylene propylene diene rubber, epichlorohydrin rubber, and nitrile rubber are preferably used.

  As the conductive agent for imparting conductivity to the conductive elastic layer, carbon black such as ketjen black and acetylene black, graphite, metal powder, conductive metal oxide, and ionic conductive agent can be used. For example, quaternary ammonium salts such as tetramethylammonium perchlorate, trimethyloctadecylammonium perchlorate, and benzyltrimethylammonium chloride are used as the ion conductive material.

  The surface layers 23Y, 23M, 23C, and 23K containing roughness particles are formed by applying a material obtained by adding roughness-imparting particles to the surface coating resin to the outside of the rubber elastic layer. The roughness imparting particles are composed of organic fine particles or inorganic fine particles, and have an average particle size of several μm to several tens of μm, and the roughness can be adjusted by the particle size, the added amount, and the coating thickness.

(B4. Power supply device)
Next, the configuration of the power supply device will be described with reference to FIG. Referring to FIG. 5, each power supply device 10Y, 10M, 10C, 10K includes DC power supplies 25Y, 25M, 25C, 25K, AC power supplies 26Y, 26M, 26C, 26K, and switches 27Y, 27M, 27C, 27K. Is provided. The control unit 70 is electrically connected to the switches 27Y, 27M, 27C, and 27K, and is configured to be able to short-circuit each AC power supply.

  Further, although the image forming apparatus 100 has a configuration in which a power supply device is provided for each charging roller, the present invention is not limited thereto. For example, a configuration in which power is supplied to each charging roller from a common power supply device may be employed.

(B5. Control unit)
Next, the configuration of the control unit 70 will be described with reference to FIG. The control unit 70 includes, as main control elements, a central processing unit (CPU) 71, a random access memory (RAM) 72, a read only memory (ROM) 73, an auxiliary storage device 74, and an interface (I / F). 75).

  The CPU 71 implements overall processing of the image forming apparatus 100 by reading and executing a program stored in the ROM 73 or the like, which will be described later. Note that the CPU 71 may be any of a microprocessor, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a digital signal processor (DSP), and other circuits having arithmetic functions.

  The RAM 72 is typically a DRAM (Dynamic Random Access Memory) or the like, and temporarily stores data and image data necessary for the CPU 71 to operate the program. Therefore, the RAM 72 functions as a so-called working memory.

  The ROM 73 is typically a flash memory or the like, and stores programs executed by the CPU 71 and various setting information related to the operation of the image forming apparatus 100.

  The auxiliary storage device 74 is typically composed of a hard disk or the like. The auxiliary storage device 74 can store a relatively large amount of data in a nonvolatile manner, and stores image data used in the image forming apparatus 100.

  The interface 75 includes charging rollers 4Y, 4M, 4C, and 4K, print head portions 5Y, 5M, 5C, and 5K, developing devices 6Y, 6M, 6C, and 6K, and density sensors 7Y, 7M, 7C, and the like. 7K is electrically connected to each of the power supply devices 10Y, 10M, 10C, and 10K, and exchanges signals with various devices.

(B6. Evaluation method of components including photoconductor)
Next, a method for detecting an abnormal state of the photoconductor and the charging roller will be described. Hereinafter, for easy understanding, monochrome printing using the image forming unit 2K will be described. However, the present invention is not limited to this, and the same control can be performed for color printing.

  The control unit 70 has two types of modes, a normal mode and an inspection mode. In the normal mode, the control unit 70 turns off the switch 27K of the power supply device 10K. As a result, the power supply apparatus 10K applies an alternating voltage obtained by superimposing an AC voltage on a DC voltage to the charging roller 4K. Operations related to basic image formation using the image forming apparatus 100 such as printing by the user are controlled by the normal mode.

  On the other hand, in the inspection mode, the control unit 70 turns on the switch 27K of the power supply device 10K. As a result, the power supply device 10K applies only a DC voltage to the charging roller 4K. As a result, abnormalities in the state of the photoconductor, the charging roller, and the like become obvious.

  FIG. 7 is a flowchart illustrating a state abnormality detection method according to the embodiment. The processing shown in FIG. 7 is realized by the CPU 71 executing a control program stored in the ROM 73. In other aspects, some or all of the processing may be performed by circuit elements or other hardware.

  In step S2, the control unit 70 determines whether or not the inspection mode is set. If it is determined that the mode is not the inspection mode (normal in step S2), the control proceeds to step S4. In step S4, the control unit 70 applies an alternating voltage to the charging roller 4K in a state where the switch 27K of the power supply device 10K is OFF, and performs an operation such as printing.

  In the normal mode, as an example, the charging bias applied to the charging roller 4K is set to sine wave, 2.5 kHz, DC bias Vdc = −550V, AC bias Vpp (difference between the maximum value and the minimum value) = 1800V. The Further, as an example, the developing bias applied to the developing roller 6KR is set to a rectangular wave, a DUTY ratio of 50%, 5 kHz, Vdc = −550V, and Vpp = 1800V. At this time, as an example, the potential difference (fogging margin) between the surface potential of the background portion of the photosensitive member and the bias potential of the developer carrying member is set to 150 V so that the fog phenomenon does not occur. The fog phenomenon is a phenomenon in which the density increases due to the toner adhering to the non-image portion that should originally be whitened by the developing operation.

  On the other hand, when the control unit 70 determines that the inspection mode is set (inspection in step S2), the control unit 70 advances the control to step S6. In step S6, the control unit 70 applies only a DC voltage to the charging roller 4K in a state where the switch 27K of the power supply device 10K is turned on, and charges the photoreceptor 3K.

  In the inspection mode, the charging bias is set to Vdc = −1100 V as an example. The developing bias is set to the same applied voltage as in the normal mode.

  Note that the absolute value of the charging bias in the inspection mode is preferably set to be larger than the absolute value of Vdc (−400 V) in the normal mode. This is because the surface potential of the photoconductor in the inspection mode is set to the same level as the surface potential of the photoconductor in the normal mode.

  Further, the charging bias (DC bias) in the inspection mode is set based on Vdc and Vpp in the normal mode. Further, when Vdc in the normal mode is fixed, the charging bias in the inspection mode may be set by the amount of displacement of Vpp.

  In step S8, the control unit 70 causes the print head unit 5K to irradiate the photosensitive member 3K with a beam according to a predetermined image pattern of the inspection image. As an example, the inspection image is a uniform halftone image with a 1 on 1 off dot pattern shown in FIG. The reason is that the abnormal state of the photoconductor or the like is expressed as the amount of displacement with respect to the reference toner density, and therefore the abnormal state of the photoconductor or the like may not be detected if the reference toner density is extremely thin / dense. Because there is. Thereby, it is possible to detect an abnormal state of the photoconductor or the like with high accuracy. The halftone image is not limited to a 1 on 1 off dot pattern, and may be a uniform pattern.

  Further, it is preferable that the horizontal width (width in the main scanning direction) of the inspection image corresponds to the horizontal width of the photoreceptor 3K. In addition, the vertical width (width in the sub-scanning direction) of the inspection image is preferably at least equal to or greater than the outer periphery of the photoreceptor 3K.

  Subsequently, the control unit 70 causes the developing device 6K to attach toner to the exposed photoreceptor 3K to form a toner image corresponding to the inspection image.

  In step S10, the control unit 70 detects the toner density formed on the photoreceptor 3K based on the detection voltage output from the density sensor 7K. In this example, this toner density is the toner density in the sub-scanning direction.

  In step S12, the control unit 70 determines whether or not the detected toner density is within a predetermined density range. This step will be described with reference to FIG.

  FIG. 9 is a diagram for explaining the change in toner density. In FIG. 9, the detection voltage of the density sensor 7K is plotted on the vertical axis, and the time is plotted on the horizontal axis. As the photoconductor 3K rotates, the rotational position on the photoconductor 3K where the density sensor 7K detects the toner density changes.

  As shown in FIG. 9A, when the inspection image shown in FIG. 8 is used, the density sensor 7K obtains a toner density of about 2.0 V at a position where there is no abnormal state in the photoreceptor 3K or the like. Therefore, in this example, as an example, the predetermined concentration range is set to 2.0V ± 0.5V.

  In FIG. 9A, since the density farthest from the reference toner density of 2.0 V is 1.6 V, the control unit 70 determines that the obtained toner density is within a predetermined density range. (YES in step S12), the control is terminated as it is.

  On the other hand, in FIG. 9B, since the density farthest from the reference toner density is 1.2 V, the control unit 70 determines that the obtained toner density is not within the predetermined density range. (NO in step S12), the control proceeds to step S14.

  In step S <b> 14, the control unit 70 displays a warning image on a display unit (not shown) of the image forming apparatus 100. The content of the warning image indicates that there is a high possibility that some state abnormality has occurred in any of the components of the photoreceptor 3K, the charging roller 4K, and the blade 11K.

  Further, since the density sensor 7K is disposed downstream of the developing device 6K, the fluctuation of the toner density takes into account the abnormal state of the developing device 6K. However, the abnormal state of the developing device 6K is not manifested by a charging method using a DC voltage. Therefore, the content of the warning image may be displayed together with the fact that some state abnormality has occurred in the developing device 6K with a low probability.

  In another aspect, the content of the warning image may be a replacement proposal for the photoreceptor unit 12K (including the photoreceptor 3K, the charging roller 4K, and the blade 11K). As a result, the user or service person who has recognized the image can smoothly prepare the photoconductor unit to be replaced, and the time loss that occurs when the photoconductor unit is replaced can be reduced.

  According to the above, in addition to the photosensitive member 3K and the charging roller 4K which are components related to the charging and electrostatic latent image forming process, the abnormal state of the blade 11K is manifested by a charging method using a DC voltage. It is possible to accurately detect the state of the component (part).

  In addition, the component evaluation method according to the present embodiment is effective even in the case where some abnormality occurs in the image pattern printed on the paper P using the image forming apparatus 100 and the cause of the abnormality is specified. Specifically, when an abnormality is detected by this method, it can be determined that there is a high possibility that the cause of the abnormality is any one of the photoconductor, the charging roller, and the blade. On the other hand, if no abnormality is detected by this method, it can be determined that the cause of the abnormality is a component (for example, a primary transfer roller or a fixing heating device) related to a process downstream from the development process.

  As a result, the user or service person can smoothly perform troubleshooting for an abnormality in the image forming apparatus 100.

  In step S12 in FIG. 7, the control unit 70 determines whether or not the detected toner density is within a predetermined density range, but the determination criterion is not limited to this. For example, the control unit 70 differentiates the detected toner density every predetermined time interval (for example, 10 msec), and when the absolute value of the obtained value (density displacement with respect to time) exceeds a reference value, It may be configured to display a warning image.

  The predetermined concentration range is fixed at 2.0 V ± 0.5 V, but may be set variably. The film thickness of the photoconductor 3K becomes thin due to the influence of the blade 11K. For this reason, the surface potential of the photoconductor may gradually change according to the film thickness of the photoconductor 3K. In this case, the toner density detected by the density sensor 7K may gradually change according to the film thickness of the photoreceptor 3K. Therefore, the control unit 70 may set a density range of ± 0.5 V as a predetermined density range with respect to the density that serves as the reference, using the detected median value of the toner density as a reference.

  In the above description, when the control unit 70 determines that the obtained toner density is within the predetermined density range (YES in step S12), the control is ended without any warning. It is not limited to this. Specifically, the control unit 70 detects a density farthest from the reference toner density (2.0 V) among the obtained toner densities, and the density, and an upper limit value and a lower limit value of a predetermined density range. The difference from the closest value is calculated. For example, in the case shown in FIG. 9A, the density farthest from the reference toner density is 1.6V, and the difference from the lower limit value of the predetermined density range is 0.1V. Based on this difference, the control unit 70 may display the deterioration degree (usable period) of the photoconductor 3K, the charging roller 4K, and the blade 11K on the display unit of the image forming apparatus 100. In another aspect, the control unit 70 may display the deterioration degree of the photoconductor unit 12K including the photoconductor 3K, the charging roller 4K, and the blade 11K based on the difference on the display unit.

<C. Embodiment 2-Judgment based on comparison with normal mode (when alternating voltage is applied)>
(C1. Overview)
In the evaluation method according to the first embodiment, although the probability is low, there is a case where the state abnormality of the component (part) is determined including the state abnormality of the developing device 6K. In this case, the evaluation method according to the first embodiment cannot identify which component of the photoreceptor unit 12K (including the photoreceptor 3K, the charging roller 4K, and the blade 11K) and the developing device 6K is the cause of the abnormality. Therefore, although the photoconductor unit 12K is replaced, there is a possibility that unnecessary components are replaced such that the image defect is not eliminated and the developing device 6K is also replaced.

  In order to prevent such unnecessary replacement of components, an evaluation method for detecting only the abnormal state of the photosensitive unit 12K without detecting the abnormal state of the developing device 6K will be described below.

  In the present embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment, and therefore details thereof will not be repeated.

(C2. Evaluation method of components including photoreceptor)
As described above, the abnormal state of the photoconductor 3K, the charging roller 4K, and the blade 11K can be made obvious by using a charging method using a DC voltage. Therefore, the toner density displacement width (hereinafter also referred to as “normal displacement width”) of the inspection image in the normal mode (charging method using an alternating voltage) and the toner density of the inspection image in the inspection mode (charging method using a DC voltage). The displacement width (hereinafter also referred to as “inspection displacement width”) is compared. When the inspection displacement width is larger than the normal displacement width, the control unit can determine that a state abnormality has occurred in any of the above-described photoreceptor 3K, charging roller 4K, and blade 11K.

  The normal displacement width and the inspection displacement width will be described with reference to FIG. FIG. 10A plots the toner density of the inspection image in the normal mode (hereinafter also referred to as “normal toner density”). In FIG. 10A, the maximum value of the normal toner density is 2.1V, and the minimum value is 1.7V. Therefore, the normal displacement width is 0.4V.

  FIG. 10B plots the toner density of the inspection image in the inspection mode (hereinafter also referred to as “inspection toner density”). In FIG. 10B, the maximum value of the inspection toner density is 2.2V, and the minimum value is 1.5V. Therefore, the inspection displacement width is 0.7V.

  At this time, since the inspection displacement width is larger than the normal displacement width, it can be determined that a state abnormality has occurred in any of the photoreceptor 3K, the charging roller 4K, and the blade 11K. Below, the control which implement | achieves this evaluation method is demonstrated.

  FIG. 11 is a flowchart illustrating an evaluation method according to the present embodiment. Since the same reference numerals as those in FIG. 7 are the same, the description thereof will not be repeated.

  In step S20, the control unit 70 charges the photosensitive member 3K by applying an alternating voltage to the charging roller 4K with the switch 27K of the power supply device 10K turned OFF. Subsequently, the control unit 70 causes the print head unit 5K to irradiate the photosensitive member 3K with a beam according to the image pattern of the inspection image. Further, the control unit 70 causes the developing device 6K to attach toner to the exposed photoreceptor 3K to form a toner image corresponding to the inspection image.

  In step S22, the control unit 70 detects the normal toner density based on the detection voltage output from the density sensor 7K.

  In step S <b> 24, the control unit 70 calculates a normal displacement width from the maximum value and the minimum value of the normal toner density, and stores the normal displacement width in the RAM 72.

  In step S26, the control unit 70 charges the photosensitive member 3K by applying only a DC voltage to the charging roller 4K while the switch 27K of the power supply device 10K is ON. Subsequently, the control unit 70 causes the print head unit 5K to irradiate the photosensitive member 3K with a beam according to the image pattern of the inspection image. Thereafter, the control unit 70 causes the developing device 6K to attach toner to the exposed photoreceptor 3K to form a toner image corresponding to the inspection image.

  In step S28, the control unit 70 detects the inspection toner density based on the detection voltage output from the density sensor 7K, and calculates the inspection displacement width from the maximum value and the minimum value of the inspection toner density.

  In step S30, the control unit 70 determines whether or not the inspection displacement width is less than the normal displacement width. When determining that the inspection displacement width is less than the normal displacement width (YES in step S30), the control unit 70 ends the control without displaying a warning image. On the other hand, when it is determined that the inspection displacement width is abnormal in the normal displacement width (NO in step S30), the control unit 70 advances the control to step S14 and displays a warning image.

  The content of the warning image indicates that some state abnormality has occurred in any of the components of the photoconductor 3K, the charging roller 4K, and the blade 11K. In another aspect, the content of the warning image may be a proposal to replace the photoreceptor unit 12K (including the photoreceptor 3K, the charging roller 4K, and the blade 11K).

  According to the above, the component evaluation method according to the present embodiment reveals the abnormal state of the blade 11K in addition to the photosensitive member 3K and the charging roller 4K, which are components related to the charging and electrostatic latent image forming process. The state of these components (parts) can be detected with high accuracy.

  Further, in the present evaluation method, when an abnormality occurs in the image pattern printed on the paper P using the image forming apparatus 100, the cause is any one of the photosensitive member 3K, the charging roller 4K, and the blade 11K. Whether or not there is can be specified. Therefore, the problem that the photoconductor unit 12K and the developing device 6K are unnecessarily replaced can be solved.

  In step S30 of FIG. 11, it is determined whether or not the inspection displacement width is less than the normal displacement width. However, the comparison object of the inspection displacement width is the normal displacement width and a predetermined concentration displacement width (for example, 0. 1V) may be added. Thereby, erroneous detection due to a measurement error can be prevented.

(C3. Modification)
Another method for preventing erroneous detection due to measurement errors will be described with reference to FIG. Since the same reference numerals as those in FIG. 11 are the same, the description thereof will not be repeated.

  If the control unit 70 determines that the inspection displacement width is equal to or greater than the normal displacement width (NO in step S30), the control proceeds to step S12, and whether or not the obtained toner density is within a predetermined density range. Judge further.

  Thus, even if it is determined in step S30 that the inspection displacement width is equal to or larger than the normal displacement width due to the measurement error, if the obtained toner density is within the predetermined density range, an abnormality is detected. Not detected. Thereby, erroneous detection due to a measurement error can be prevented.

  FIG. 13 shows a functional block of the CPU 71 for executing control according to this modification. Referring to FIG. 13, CPU 71 includes a displacement width detection unit 81, comparison unit 82, and determination unit 83.

  The displacement width detector 81 receives the normal toner density and the inspection toner density from the density sensor 7K. The displacement width detection unit 81 specifies the maximum value and the minimum value of the normal toner density, calculates the normal displacement width, and outputs the normal displacement width to the RAM 72. Subsequently, the displacement width detection unit 81 specifies the maximum value and the minimum value of the inspection toner density, calculates the inspection displacement width, and outputs the inspection displacement width to the comparison unit 82.

  The comparison unit 82 acquires the normal displacement width from the RAM 72 and compares whether or not the inspection displacement width is less than the normal displacement width. Subsequently, the comparison unit 82 outputs the comparison result to the determination unit 83.

  When the comparison result that the inspection displacement width is less than the normal displacement width is input from the comparison unit 82, the determination unit 83 does not display the warning image on the display unit.

  On the other hand, when a comparison result indicating that the inspection displacement width is equal to or larger than the normal displacement width is input from the comparison unit 82, the determination unit 83 acquires the inspection toner density and the predetermined density range acquired from the RAM 72. Subsequently, the determination unit 83 determines whether or not the inspection toner density is within a predetermined density range. If the determination unit 83 determines that the inspection toner density is within the predetermined density range, the determination unit 83 does not display the warning image on the display unit. On the other hand, when the determination unit 83 determines that the inspection toner density is not within the predetermined density range, the determination unit 83 displays a warning image on the display unit.

<D. Embodiment 3-Identifying Cause Component>
(D1. Overview)
Image irregularities are periodically generated in the image patterns shown in FIGS. 2B, 2D, and 2F. This period is due to the fact that the photosensitive member 3K, the charging roller 4K, and the developing roller 6KR are rotating bodies, and corresponds to the rotational period (outer periphery) of any one of these components.

  Therefore, by analyzing the period in which image unevenness (toner density unevenness) occurs, it is possible to identify the component in which the state abnormality has occurred.

  FIG. 14 is a diagram for explaining a change in toner density. In FIG. 14, as an example, it is assumed that the photoconductor 3 </ b> K is scratched and the charging roller 4 is soiled. Under these influences, toner density exceeding a predetermined density range appears periodically.

  The degree of deviation (density unevenness) of the obtained toner density from the reference density (2.0 V) varies depending on the cause of the abnormality. In the example shown in FIG. 14, the toner density of the portion where the surface potential of the photosensitive member 3K is disturbed due to the contamination of the charging roller 4 becomes 1.1V, and the toner concentration of the portion where the surface potential is disturbed due to the scratch of the photosensitive member 3K. Is assumed to be 1.4V.

  In this case, the period T1 at which the toner density becomes 1.1 V is a period corresponding to the outer periphery of the charging roller 4K. More specifically, when the period T1 is multiplied by the rotation speed of the photosensitive member 3K, the outer periphery of the charging roller 4K is obtained. The period T2 at which the toner density becomes 1.4 V is a period corresponding to the outer periphery of the photoreceptor 3K.

  For this reason, by acquiring a period in which the toner density exceeds the predetermined density range and the toner density of the same level is generated, it is possible to identify the component in which the state abnormality has occurred.

(D2. Evaluation method of components)
A specific control flow for realizing the above will be described with reference to FIG. Note that portions denoted by the same reference numerals as those in FIG. 7 are the same and will not be described repeatedly. Further, in the present embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment, and therefore details thereof will not be repeated.

  If the controller 70 determines that the obtained toner density is not within the predetermined range (NO in step S12), the control proceeds to step S42.

  In step S42, the control unit 70 determines whether or not the position (timing) for detecting the toner density exceeding the predetermined density is periodic. More specifically, the control unit 70 stores a toner density exceeding a predetermined density and a position (timing) for detecting the toner density in the RAM 72 in association with each other. Further, it is determined whether or not the position where the same toner density is detected is periodic.

  When the control unit 70 determines that the position where the toner density of the same level is detected is not periodic (NO in step S40), the control unit 70 displays a warning image in step S14 and ends the control.

  On the other hand, when it is determined that the position at which the same toner density is detected is periodic (NO in step S40), control unit 70 determines in step S42 whether or not the detected period corresponds to a predetermined period. Judging.

  As an example, the predetermined cycle is a cycle corresponding to the outer circumference (rotation cycle) of the photoreceptor 3K, the charging roller 4K, and the developing roller 6KR.

  When it is determined that the detected cycle does not correspond to the predetermined cycle (NO in step S42), control unit 70 displays a warning image in step S14 and ends the control.

  On the other hand, when determining that the detected cycle corresponds to the predetermined cycle (YES in step S42), control unit 70 specifies the cause and displays a warning image in step S44.

  More specifically, the control unit 70 is configured to cause a state abnormality by specifying whether the detected cycle corresponds to the outer periphery of the photoreceptor 3K, the charging roller 4K, or the developing roller 6KR. Identify the element. Subsequently, the control unit 70 displays that a certain state abnormality has occurred in the identified component.

  Based on the above, it is possible to more specifically identify the component caused by the state abnormality. For example, when it is determined that the photoconductor 3K is in an abnormal state, the replacement of unnecessary components can be suppressed by replacing only the photoconductor 3K instead of replacing the entire photoconductor unit 12K.

<E. Embodiment 4-Visual inspection>
(E1. Overview)
By using a line sensor as the density sensor, it is possible to detect a state abnormality (density change) in a wide area in the main scanning direction in the toner image. However, since line sensors are expensive, it is preferable to avoid mounting them on inexpensive industrial products.

  On the other hand, when a density sensor having only one or a small number of light receiving elements is used, there is a possibility that density unevenness as shown in FIGS. 2C, 2D, and 2F cannot be detected.

  Therefore, a method for visually evaluating the state of components such as a photoreceptor will be described below. In the present embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment, and therefore details thereof will not be repeated.

(E2. Visual evaluation method)
FIG. 16 is a flowchart for explaining a visual evaluation method. Since the same reference numerals as those in FIG. 11 are the same, the description thereof will not be repeated.

  Referring to FIG. 16, in step S20, control unit 70 exposes and develops the inspection image on the photoconductor in the normal mode (charging method using an alternating voltage), and in step S50, the exposed inspection image is printed on paper P. Print.

  In step S26, the control unit 70 exposes and develops the inspection image on the photoconductor in the inspection mode (charging method using only DC voltage), and prints the exposed inspection image on the paper P in step S52.

  In step S54, the user or the service person visually inspects the image patterns printed in the normal mode and the inspection mode to perform inspection.

  In step S56, the user or service person determines whether there is an abnormality in the image printed in the inspection mode. More specifically, it is determined that there is an abnormality when the density unevenness in the image printed in the inspection mode is larger than the density unevenness in the image printed in the normal mode.

  When the user or the service person determines that there is an abnormality in the image printed in the inspection mode (YES in step S56), the photoconductor unit 12K is replaced or the photoconductor unit 12K has reached the end of its life in step S58. To the image forming apparatus 100.

  When the user or the service person determines that there is no abnormality in the image printed in the inspection mode (NO in step S56), the inspection ends.

  According to the above, whether or not a state abnormality has occurred in any of the photoconductor, the charging roller, and the blade can be determined by simply comparing the printed images without providing an expensive line sensor in each image forming unit. Judgment can be made.

  Further, by using the halftone image shown in FIG. 8 as the inspection image, the human eye can recognize the density change with high sensitivity.

(E3. Modified Example 1-Image Pattern)
When there are a plurality of image forming units (2Y, 2M, 2C, 2K) as in the image forming apparatus 100, a visual inspection is performed using an inspection image as shown in FIG. This inspection image has a region printed using only yellow toner from the top, and subsequently a region printed using only magenta, cyan, and black toners. In each area, a halftone image pattern as shown in FIG. 8 is printed. The vertical width of each region (width in the sub-scanning direction) is printed at a distance corresponding to at least the outer periphery of the photoconductor.

  As a result, the user or service person can specify the image forming unit in which the state abnormality has occurred by simply performing the printing twice (printing in the inspection mode and the normal mode) and comparing the printed images. Can do.

(E4. Modification 2-Scanner)
In the above example, the images printed in the inspection mode and the normal mode are compared visually, but the present invention is not limited to this. For example, the inspection shown in the first to third embodiments may be performed by reading a printed image with a scanner (line sensor attached to the scanner).

  Thereby, since it can test | inspect widely in the main scanning direction using the line sensor of a scanner, it can test | inspect with high precision rather than visual inspection. In addition, since it is not necessary to provide a line sensor in the image forming unit of the image forming apparatus 100, the production cost of the image forming apparatus 100 can be reduced.

<F. Embodiment 5-Inspection on Intermediate Transfer Member>
In the above embodiment, density sensors (7Y, 7M, 7C, 7K) are provided in the image forming units (2Y, 2M, 2C, 2K). As a result, it can be determined that the cause of the state abnormality is caused in the process upstream of the primary transfer, but the production cost of the image forming apparatus 100 is increased.

  Therefore, in this embodiment, a single density sensor 13 is used to inspect the abnormal state of each image forming unit. Specifically, the density sensor 13 is disposed at a position facing the intermediate transfer belt driving roller 14 and detects the density of the toner image primarily transferred to the intermediate transfer belt 1.

  The inspection method according to the present embodiment performs the inspection according to the above-described embodiment using the inspection image shown in FIG. As a result, it is possible to inspect the abnormal state of each image forming unit using one density sensor without providing a density sensor in each image forming unit, so that the production cost of the image forming apparatus 100 can be reduced. .

  The density sensor 13 detects the toner density on the intermediate transfer belt 1 whose behavior is stabilized by being pressed by the intermediate transfer belt driving roller 14. Thereby, the density sensor 13 can detect the toner density with high accuracy without being affected by vibration or the like.

  It is also possible to provide a program that causes a computer to function and execute control as described in the above flow. Such a program is recorded on a non-temporary computer-readable recording medium such as a flexible disk attached to the computer, a CD-ROM (Compact Disk-Read Only Memory), a RAM, a ROM, and a memory card, and the program product Can also be provided. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built in the computer. A program can also be provided by downloading via a network.

  The program may be a program module that is provided as part of an operating system (OS) of a computer and that calls necessary modules in a predetermined arrangement at a predetermined timing to execute processing. In that case, the program itself does not include the module, and the process is executed in cooperation with the OS. A program that does not include such a module can also be included in the program according to the present invention.

  The program according to the present invention may be provided by being incorporated in a part of another program. Even in this case, the program itself does not include the module included in the other program, and the process is executed in cooperation with the other program. Such a program incorporated in another program can also be included in the program according to the present invention.

  The provided program product is installed in a program storage unit such as a hard disk and executed. The program product includes the program itself and a recording medium on which the program is recorded.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 Intermediate transfer belt, 2Y, 2M, 2C, 2K image forming unit, 3Y, 3M, 3C, 3K photoconductor, 4Y, 4M, 4C, 4K charging roller, 5Y, 5M, 5C, 5K print head, 6Y, 6M , 6C, 6K Developer, 6YR, 6MR, 6CR, 6KR Developing roller, 7Y, 7M, 7C, 7K Density sensor, 8Y, 8M, 8C, 8K Primary transfer roller, 9Y, 9M, 9C, 9K Cleaning roller, 10Y , 10M, 10C, 10K power supply device, 11Y, 11M, 11C, 11K blade, 12Y, 12M, 12C, 12K photosensitive unit, 14 intermediate transfer belt driving roller, 70 control unit, 72 RAM, 73 ROM, 74 auxiliary storage device 75 interface, 81 displacement width detection unit, 82 comparison unit, 83 determination unit, 100 image forming apparatus.

Claims (16)

A method for evaluating a state of a component related to a process including at least charging and formation of an electrostatic latent image, which is used for image formation according to an electrophotographic method,
Applying a first DC voltage to charge the image carrier;
Exposing the image carrier charged by application of the first DC voltage in a uniform pattern;
Forming a first toner image corresponding to the uniform pattern by attaching toner to the exposed image carrier;
Detecting a density in the sub-scanning direction at a predetermined position in the main scanning direction of the first toner image, and calculating a displacement width of the density from the detected maximum value and minimum value;
Applying an alternating voltage including a second DC voltage and an AC voltage to charge the image carrier;
Exposing the image carrier charged by application of the alternating voltage with the uniform pattern;
Forming a second toner image corresponding to the uniform pattern by attaching toner to the image carrier charged by application of the alternating voltage and exposed in the uniform pattern;
Detecting a density in the sub scanning direction at a predetermined position in the main scanning direction of the second toner image, and calculating a displacement width of the density from the detected maximum value and minimum value;
When the displacement width of the density calculated for the first toner image is greater than or equal to the displacement width of the density calculated for the second toner image, a warning indicating that an abnormality has occurred in the component Displaying the screen . Further comprising setting a predetermined density range in association with the uniform pattern;
The step of displaying the warning screen is a case where a displacement width of the density calculated for the first toner image is equal to or larger than a displacement width of the density calculated for the second toner image, and The method according to claim 1 , wherein the warning screen is displayed when a density change in the sub-scanning direction at a predetermined position in the main scanning direction of the first toner image is not within the predetermined density range. Step, based on the displacement amount of density change in said second toner image, comprising determining the predetermined concentration range, The method according to claim 2 for setting pre SL. The absolute value of the first DC voltage, the greater than the absolute value of the second DC voltage, the method according to any one of claims 1 to 3. The value of the first DC voltage, the second set based on the amplitude values and the AC voltage of the DC voltage, the method according to any one of claims 1 to 4. The difference between the pre-Symbol lower limit of the minimum value and the predetermined density range in the concentration of the differential or the first toner image, the upper limit of the maximum value and the predetermined density range in the concentration of the first toner image based further comprising the step of determining the degree of deterioration of the component, the method according to claim 2 or 3. If the concentration in the sub-scanning direction before Symbol first toner image is determined not to fall within the predetermined concentration range, whether the predetermined concentration range and a position corresponding to a predetermined period Moreover, further comprising the step of determining,
The predetermined cycle includes a cycle corresponding to at least one of a rotation cycle of a component rotating in contact with the image carrier and a rotation cycle of the image carrier among the components. Item 4. The method according to Item 2 or 3 . If the previous SL predetermined concentration range position is determined to correspond to a predetermined cycle, further comprising the step of identifying the components has deteriorated from the corresponding predetermined cycle, the method according to claim 7. And printing the previous SL first toner image on the first recording medium,
The method according to claim 1, further comprising: printing the second toner image on a second recording material .   The method according to claim 1, wherein the component includes the image carrier and a charging device for charging the image carrier.   The method according to claim 10, wherein the component further includes a developing device for attaching a toner image to the image carrier. The method according to claim 1, wherein the density of the first toner image and the density of the second toner image are densities of a toner image formed on the image carrier. The image forming apparatus includes an intermediate transfer member that receives and conveys a toner image formed on the image carrier and transfers the toner image to a recording medium.
12. The method according to claim 1, wherein the density of the first toner image and the density of the second toner image are the density of the toner image transferred to the intermediate transfer member.   The method according to claim 1, wherein the uniform pattern is a pattern composed of halftones. A program that causes a computer of an apparatus that performs the image formation to execute the method according to claim 1 . An electrophotographic image forming apparatus,
A control unit;
A display unit;
An image carrier for carrying a toner image;
A charging device for charging the image carrier;
A power supply device for applying a first DC voltage to the charging device;
An exposure apparatus that exposes the image carrier charged by the application of the first DC voltage in a uniform pattern;
And a developing device for forming a first toner image corresponding to the uniform pattern by adhering toner to the image bearing member is the exposure,
The power supply device applies an alternating voltage including a second DC voltage and an AC voltage to the charging device,
The exposure apparatus exposes the image carrier charged by the application of the alternating voltage in the uniform pattern,
The developing device forms a second toner image corresponding to the uniform pattern by adhering toner to an image carrier charged by the application of the alternating voltage and exposed in the uniform pattern;
The controller is
By detecting the density in the sub-scanning direction at a predetermined position in the main scanning direction of the first toner image, the displacement width of the density is calculated from the detected maximum value and minimum value of the density,
By detecting the density in the sub-scanning direction at a predetermined position in the main scanning direction of the second toner image, the displacement width of the density is calculated from the detected maximum value and minimum value of the density,
If the displacement width of the density calculated for the first toner image is greater than or equal to the displacement width of the density calculated for the second toner image, it relates to a process including at least charging and formation of an electrostatic latent image. An image forming apparatus that causes the display unit to display a warning screen indicating that an abnormality has occurred in a constituent element.